1. Field of the Invention
This invention relates to a relay. In particular, this invention relates to a relay of the type having an excitation coil; a U-shaped yoke comprising a leg serving as the core of said excitation coil, a free leg, and a bridge connecting said legs; a contact carrier unit which is attached to said free leg of said yoke; a supporting bridge associated with said contact carrier unit and extending essentially perpendicularly to the axis of said excitation coil; at least one switching contact having contact fingers, said contact fingers being supported by said supporting bridge; an armature for operatin said switching contact, said armature having an armature leg for interacting with said core of said excitation coil, and a free armature leg not interacting with said core of said excitation coil; a knife-edge bearing for said armature, said knife-edge bearing formed by one edge of a face end of said free leg of said yoke; and a holding element for attaching said armature to said free leg of said yoke.
2. Description of the Prior Art
Such a relay is commercially available. This relay has an armature in the form of a plate which is placed perpendicularly to the axis of the excitation coil and perpendicularly to the free leg of the yoke. Two holding bolts serve as the holding element. They extend perpendicularly to the plane of the armature and penetrate the same. The holding bolts are pressed against the free leg of the yoke by a pressing plate and a screwing device. Operating fingers of said armature are located at that end which is positioned away from the core of the excitation coil. These fingers project beyond the free leg of the yoke. A large contact carrier unit surrounds the activating unit consisting of the excitation coil, of the yoke, and of an armature, on four sides. This activating unit is connected by two screws to the free leg of the yoke. The contact carrier unit contains a supporting bridge extending perpendicularly to the axis of the excitation coil. On this unit there are attached various plates made of an insulating material by two screw connections. The contact fingers of several switching contacts are inserted between the insulating plates. The contact fingers extend perpendicularly to the axis of the excitation coil. The contact fingers exceed significantly beyond the operating fingers of the armature. Therefore, this conventional relay requires considerable space. Furthermore, it is rather expensive to assemble this relay due to the multitude of screwing connections.
Another relay which is also commercially available has a cylindrical excitation coil with a cylindrical core. On one side, the core of the excitation coil reaches beyond the spool flange. It is riveted to a plate made of insulating material. The foot of an L-sahped yoke rests against the protruding end of the core of the excitation coil. It is clamped in between said one spool flange and the insulating plate. The yoke with its outer face end which faces away from the coil engages a shoulder of the insulating plate. The extension of this plate simultaneously serves as a contact carrier for three contact fingers of a switching contact which are placed one behind the other. At its end side, the free leg of the yoke contains a rectangular hole through which protrudes an angular armature. The free leg of the armature extends essentially parallel to the free leg of the yoke. A tension spring which is attached in the recess of the yoke serves as a holding element for the armature. The spring presses the armature against an edge of the face end of the free leg of the yoke. Thus, this edge serves as a knife-edge bearing. The free leg of the armature contains a centrally located recess so as to form two lateral armature operating fins which are connected to each other by a bridge made of insulating material. This bridge has a centrally located recess into which meshes a basically cross formed operating element. This element passes through an opening in the contact finger of an alternating contact. Together with the cross beam of the cross form, it engages the middle contact finger. In this relay an optimal guidance of the magnetic flux is not achieved, due to the air gap between the core of the excitation coil and the L-shaped yoke. Therefore, its control requires a substantial amount of power. This relay has a considerable height, because the spool unit of the excitation coil is supported by the contact carrier unit formed as an insulating plate.